<form action="<?php bloginfo('siteurl'); ?>" id="searchform" method="get"  class="frm_search">
    <div>
        <!--<label for="s" class="screen-reader-text">Search for:</label>-->
        <input type="text" id="s" class="txt_search" name="s" value="tìm kiếm tin tức" onblur="if(this.value=='') this.value='tìm kiếm tin tức';" onfocus="if(this.value=='tìm kiếm tin tức') this.value='';" />
        
        <input type="submit" value="" class="btn_tim" id="searchsubmit" />
    </div>
</form>